Turn from Sticky to Slippery Surface

Synthetic polymer membranes are used in a variety of applications based on the science of "bioseparation" - filtering specific proteins from complex liquid mixtures of biological molecules. But proteins often stick to these membranes, clogging up their pores and severely limiting their performance, according to Georges Belfort, the Russell Sage Professor of Chemical Engineering at Rensselaer and corresponding author of the paper.

Operators need an inexpensive way to clean these membranes while they are still in place, rather than periodically removing them from the application environment, Belfort says. But currently the only cleaning options involve expensive chemicals or labor-intensive procedures that result in significant process down-time.

To make the new materials, Belfort and his co-workers attached spiropyran molecules to a widely used industrial polymer, poly(ether sulfone). Spiropyrans are a group of light-switchable organic molecules that exist in a colourless, "closed" form under visible light, but switch to a reddish-purple, "open" form when exposed to UV light. This change leads to an alteration of the new material's polarity, or the chemical structure of its atoms.

In switching from non-polar to polar, the material becomes less attractive to proteins that might stick to its surface, according to Belfort. Exposing the material to UV light is like flipping a molecular switch, causing sticky proteins to detach from the surface and wash away in the liquid, the researchers report.

In addition to bioseparations, Belfort envisions a number of potential applications for the materials, ranging from new membranes for treating polluted water to the targeted release of drugs in the body.